Transplants of Microvascular Bundles – Source of Neoangiogensis and Revascularisation. Summary of the Doctoral Thesis

Abstract

Implantation of vascular bundles into ischemic tissue as a means of revascularization has been performed for many decades, but there is considerable confusion regarding its clinical utility. We believe that the varying results quoted in the literature are a result of using bundles that are different from each other. We propose that vascular bundles are of 2 types: a parallel pipe type and an axial flap type. We propose that in rats, the saphenous arteriovenous bundle represents a parallel pipe type and the epigastric bundle an axial flap type. If ligated and implanted into an isolated sterile environment, the parallel pipe type of vascular bundle will thrombose, whereas the axial flap type of bundle will remain patent and demonstrate neovascular sprouting. Methods. The study was carried out in 24 rats (48 bundles). Saphenous and epigastric bundles were dissected, ligated with 10-0 nylon, and implanted into a tubing of sterile silicone sheet tube. The bundles were analyzed at various time intervals by both gross and histologic examination. Results. The femoral bundle did not demonstrate any arteriovenous cross-communication under magnification, confirming its status as a parallel pipe type. The epigastric bundle demonstrated a rich plexus of arteriovenous channels, confirming its status as an axial flap type. A distinct adherent thrombus was seen at 24 hours in all the ligated femoral bundles and was still present at 3 weeks; none of these demonstrated evidence of neovascular sprouting. The ligated epigastric bundles remained patent in all specimens with no evidence of thrombosis, and all demonstrated exuberant neovascular sprouting. Conclusions. Our experiment establishes that there are at least 2 distinct types of avascular bundles in the rat. It also indicates that parallel pipe type of vascular bundles implanted into latex tubing thrombose and do not demonstrate neovascularization. On the other hand, under the same circumstances “axial flap” bundles remain patent and demonstrate exuberant neovascularization. Only “axial flap” can be used for revascularization of avascular tissues.